It seems to just be the closing tag for the metadata element. Isn't that odd?

that is where it defaults if it gets totally lost in the file somewhere. It is likely it got lost because an earlier thing was never closed such as a quote mark or tag. It might also be at the end if a required element isn't there.

1 The meta block has no error. It passes ePubCheck as I tested.
2 If there's unclosed tag, ePubCheck will show
ERROR: /OPS/content.opf(19): XML document structures must start and end within the same entity.